Increased electric machine capability during engine start

Abstract

A powertrain controller for a vehicle may include input channels configured to receive start requests for an engine and operating condition data for an electric machine, and output channels configured to provide torque commands for the electric machine. The powertrain controller may further include control logic configured to, in response to receiving a start request for the electric machine while the operating condition data indicates that the electric machine is operating at a torque limit to drive the vehicle, generate torque commands that cause the electric machine to exceed the torque limit.

What is claimed is: 
     
         1 . A method of controlling a vehicle comprising:
 in response to receiving a start request for an engine while an electric machine is generating torque to drive the vehicle at a torque limit of the electric machine, increasing the torque beyond the torque limit for a predefined duration of time to provide torque to start the engine.   
     
     
         2 . The method of  claim 1 , wherein the predefined duration of time is less than a duration of time to start the engine. 
     
     
         3 . The method of  claim 2 , wherein the predefined duration of time is less than 1.5 seconds. 
     
     
         4 . The method of  claim 1 , further comprising permitting current from a battery powering the electric machine to exceed a discharge limit during the predefined duration of time. 
     
     
         5 . The method of  claim 1 , further comprising in response to the start request, commanding the electric machine to provide a total torque greater than the torque limit. 
     
     
         6 . A vehicle comprising:
 an engine;   a traction motor; and   a controller configured to, in response to receiving a request for additional torque to start the engine while the traction motor is operating at a torque limit to satisfy a drive torque command, command the traction motor to increase torque output for a predefined duration of time to satisfy the request for additional torque.   
     
     
         7 . The vehicle of  claim 6 , wherein the additional torque is equal to a start torque for the engine. 
     
     
         8 . The vehicle of  claim 6 , wherein the predefined duration of time is less than a duration of time to start the engine. 
     
     
         9 . The vehicle of  claim 8 , wherein the predefined duration of time is approximately 1 second. 
     
     
         10 . The vehicle of  claim 6 , further comprising a traction battery configured to power the traction motor, wherein the controller is further configured to, in response to receiving the request, command current from the fraction battery at a magnitude exceeding a discharge limit of the traction battery. 
     
     
         11 . A powertrain controller for a vehicle comprising:
 input channels configured to receive start requests for an engine and operating condition data for an electric machine;   output channels configured to provide torque commands for the electric machine; and   control logic configured to, in response to receiving a start request for the electric machine while the operating condition data indicates that the electric machine is operating at a torque limit to drive the vehicle, generate torque commands that cause the electric machine to exceed the torque limit.   
     
     
         12 . The controller of  claim 11 , wherein the generated torque commands cause the electric machine to exceed the torque limit for a predefined duration of time less than a duration of time to start the engine. 
     
     
         13 . The controller of  claim 12 , wherein the predefined duration of time is approximately 1 second. 
     
     
         14 . The controller of  claim 11 , wherein the output channels are further configured to provide current commands for a fraction battery configured to power the electric machine and wherein the control logic is further configured to, in response to receiving the start request, generate current commands that cause the traction battery to exceed a discharge limit during the predefined duration of time.